Zinit: simplify setup

.config/shell/zinit.zsh

@@ -2,15 +2,10 @@
 # Zinit Options & Plugins
 ##################################
 
-if [[ ! -f $HOME/.local/share/zinit/zinit.git/zinit.zsh ]]; then
-    print -P "%F{33} %F{220}Installing %F{33}ZDHARMA-CONTINUUM%F{220} Initiative Plugin Manager (%F{33}zdharma-continuum/zinit%F{220})…%f"
-    command mkdir -p "$HOME/.local/share/zinit" && command chmod g-rwX "$HOME/.local/share/zinit"
-    command git clone https://github.com/zdharma-continuum/zinit "$HOME/.local/share/zinit/zinit.git" && \
-        print -P "%F{33} %F{34}Installation successful.%f%b" || \
-        print -P "%F{160} The clone has failed.%f%b"
-fi
-
-source "$HOME/.local/share/zinit/zinit.git/zinit.zsh"
+ZINIT_HOME="${XDG_DATA_HOME:-${HOME}/.local/share}/zinit/zinit.git"
+[ ! -d $ZINIT_HOME ] && mkdir -p "$(dirname $ZINIT_HOME)"
+[ ! -d $ZINIT_HOME/.git ] && git clone https://github.com/zdharma-continuum/zinit.git "$ZINIT_HOME"
+source "${ZINIT_HOME}/zinit.zsh"
 
 zinit snippet PZTM::directory